1. Field of the Invention
This invention relates to a substrate processing apparatus and a method for manufacturing a semiconductor device, and particularly to a substrate processing apparatus the lower structure of which is improved.
2. Description of the Related Art
A conventional substrate processing apparatus for performing a method for manufacturing a semiconductor device, for example, when taking a vertical CVD apparatus as an example and explaining with the use of a view for illustrating principal portions of FIG. 5, is as follows.
An outer reaction tube 1 is provided inside of a heater which is not shown in the drawing. Within the outer reaction tube 1, there is concentrically provided an inner reaction tube 2 for constructing a processing space 19 with an upper end being opened. The outer reaction tube 1 and the inner reaction tube 2 are vertically disposed on a flange 3. A lower end of the outer reaction tube 1 is sealed by an upper end of the flange 3 via an O-ring 17. A lower opening of the flange 3 is airtightly covered with a furnace opening cover 19 via an O-ring 18.
The flange 3 is provided with a coolant flow passage 5 that allows a cooling water for cooling the above-mentioned O-ring 17 to flow therethrough, and a periphery of the O-ring 17 is water-cooled. In addition, the furnace opening cover 19 is provided with a coolant flow passage 6 that allows a cooling water for cooling the above-mentioned O-ring 18 to flow therethrough, and the periphery of the O-ring 18 is water-cooled. A boat which is not shown in the drawing is vertically disposed on the furnace opening cover 19, and the boat is inserted into the inner reaction tube 2. In the boat, wafers to be processed are loaded being horizontally oriented in a multi-storied fashion.
The flange 3 is provided with an exhaust opening 4. This exhaust opening 4 communicates with a lower end of a cylindrical space 13 formed as an exhaust path between the outer reaction tube 1 and the inner reaction tube 2 and through the exhaust opening 4, interiors of the outer reaction tube 1 and the inner reaction tube 2 are exhausted. Moreover, the flange 3 is also designed to be provided with a gas introducing nozzle in such a way that a reaction gas is introduced into the inner reaction tube 2, which is not shown in the drawing.
The boat is moved down via the furnace opening cover 19 by a boat elevator which is not shown in the drawing, and wafers are loaded onto the boat, and then, the boat is inserted into the inner reaction tube 2 by the boat elevator. After the furnace opening cover 19 completely covers a lower end of the flange 3, the interiors of the outer reaction tube 1 and the inner reaction tube 2 are exhausted to a reduced pressure.
While supplying a reaction gas into the inner reaction tube 2 from the gas introducing nozzle, the reaction gas is exhausted from the exhaust opening 4. The interior of the inner reaction tube 2 is heated to a prescribed temperature, and a film is formed onto a surface of the wafers. After completing the film formation, an inert gas is introduced from the gas introducing nozzle so that the atmosphere inside of the outer reaction tube 1 and the inner reaction tube 2 is substituted for the inert gas, and then, the interiors of the outer and inner tubes 1 and 2 are returned to a normal pressure to draw out the boat.
In the mean time, in contrast to the above-mentioned CVD apparatus, a process, such as annealing, diffusion or oxidation, in a furnace of a substrate processing apparatus (hereafter referred to as a diffusion furnace and the like) is performed at a higher temperature (1000xc2x0 C. or more). In addition, there are many devices wherein metal contamination should be avoided. For these reasons, a metal member can not be used inside of a furnace such as a diffusion furnace and the like. All of a reaction tube, a flange, a cover body and the like are typically formed of quartz without using a metal part.
On the other hand, a process in the CVD apparatus is performed at a lower temperature (about 600 to 750xc2x0 C.) so that, even if a metal member is used in a furnace, a mulfunction is not caused to the extent as in the diffusion furnace and the like. Therefore, in general, metal such as stainless steel, aluminum alloy or the like which has more superior machinability and cost efficiency is used for the flange and the furnace opening cover while quartz is used for the outer reaction tube 1 and the inner reaction tube 2.
In this way, a metal member is used for some parts of the furnace in a vertical CVD apparatus, but a relation between the metal flange and an exhaust gas particularly causes a problem in this case. In the conventional vertical CVD apparatus, as mentioned above, the metal flange 3 is provided with the exhaust opening 4, and the outer reaction tube 1 and the metal flange 3 are sealed by the O-ring 17. As a material of the O-ring 17, there is generally used a fluororubber or the like which has durability and elasticity. In the case of fluororubber, when using this under a reduced pressure at a low temperature of about 600 to 750xc2x0 C., a component such as water and the like is released by heating so that an organic contaminant referred to as degasification is generated. Therefore, the metal flange 3 is provided with the coolant flow passage 5 to allow cooling water to flow therethrough so that the periphery of the O-ring 17 is cooled.
However, when allowing cooling water to flow through the coolant flow passage 5 with which the metal flange 3 is provided in order to water-cool the O-ring 17, the entire metal flange 3 including the exhaust opening 4 becomes cooled, because the metal flange 3 formed integrally with the exhaust opening 4 is formed of metal such as stainless steel and the like. If the entire metal flange 3 has been cooled, the reaction gas is cooled by contact with the metal flange 3 when being exhausted from the exhaust opening 4 provided for the metal flange 3 so that reaction by-products adhere to a metal flange inner wall. Many of the reaction by-products adhere particularly to the vicinity of the exhaust opening 4. The reaction by-products which have adhered peel off to be particles which contaminate the reaction atmosphere so that there is a fear of adherence of the particles onto the substrates. The adherence of the particles onto the substrates tends to become a cause of defects in a product (a semiconductor device).
Hence, in order to take measures against the by-products, an attempt to heat the portion of the metal flange 3 except the vicinity of the O-ring 17 has been made. However, a metal component is released from a metal surface by heating and an organic contaminant referred to as degasification is generated, which results in metal contamination. In CVD, metal contamination is undesirable, although the suppression of the metal contamination is not so required to the extent as in the diffusion furnace and the like. Therefore, a measure to heat a metal flange can not be adopted. As a result, it is impossible to effectively prevent the reaction by-products from adhering to the metal flange 3.
Thus, it is impossible to effectively prevent the reaction by-products from adhering to the inner wall of the metal portion due to the cooling phenomenon of the metal portion. As a result, in order to remove the reaction by-products, there has been a problem that a maintenance period of an apparatus becomes short.
An object of the present invention is to provide a substrate processing apparatus and a method for manufacturing a semiconductor device wherewith, by resolving the problems with the prior art noted in the foregoing, reaction by-products are less apt to adhere to a metal portion so that a maintenance period is long
A first invention resides in a substrate processing apparatus comprising: a nonmetal reaction tube; a heater that heats an interior of the reaction tube to a prescribed processing temperature; a metal flange for disposing the reaction tube thereon, that constitutes a furnace opening of the reaction tube; a furnace opening cover for covering the furnace opening of the metal flange; a gas introducing opening provided for the metal flange, for introducing a reaction gas into the reaction tube; and an exhaust opening integrally provided for the reaction tube, for exhausting the interior of the reaction tube, wherein a substrate is processed in the reaction tube.
While being supplied into a reaction tube from a gas introducing opening, a reaction gas is exhausted from an exhaust opening. This exhaust opening is integrally provided for the reaction tube disposed on a metal flange. Accordingly, even if the metal flange is cooled, the reaction gas is exhausted before the reaction gas reaches the metal flange so that the reaction gas which remains in a high temperature state without being cooled by the metal flange is exhausted to an outside. As a result, it is possible to effectively prevent reaction by-products resulting from a cooling phenomenon from adhering to a periphery of the exhaust opening or an inner wall of the metal flange so that particles are not generated onto a substrate during processing the substrate.
In the above-mentioned invention, it is preferable that the prescribed processing temperature be from 600 to 750xc2x0 C., and that the substrate be processed under a reduced pressure. A typical process for processing a substrate at a temperature from 600 to 750xc2x0 C. under a reduced pressure includes a CVD process. In the case of performing a process at such temperatures, even if a metal member such as a metal flange and the like is used at a lower portion of an apparatus (a lower furnace portion), a problem of metal contamination does not arise because the temperature is low.
A second invention resides in a substrate processing apparatus comprising: a nonmetal reaction tube in which a substrate is processed; a gas introducing opening for introducing a reaction gas into the reaction tube; a heater that heats an interior of the reaction tube to a prescribed processing temperature; a metal flange for disposing the reaction tube thereon via an O-ring, that constitutes a furnace opening of the reaction tube; a furnace opening cover for covering the furnace opening of the metal flange; a coolant flow passage provided for the metal flange, that allows a cooling medium for cooling the O-ring to flow therethrough; and an exhaust opening integrally provided to the reaction tube, for exhausting the interior of the reaction tube, wherein a gas after processing the substrate in the reaction tube is exhausted from the exhaust opening before passing through the O-ring.
Since an exhaust opening is provided to a reaction tube itself disposed on a metal flange, a reaction gas is exhausted from the exhaust opening provided to the reaction tube before the reaction tube passes through an O-ring disposed between the reaction tube and the metal flange. Accordingly, the reaction gas which remains at a high temperature is exhausted from the exhaust opening without being cooled by contact with the metal flange which becomes cooled as the O-ring is cooled by flowing a cooling medium. As a result, it is possible to effectively prevent reaction by-products resulting from the cooling from adhering to a periphery of the exhaust opening or an inner wall of the metal flange.
A third invention reside in a method for manufacturing a semiconductor device, comprising forming a semiconductor device in a nonmetal reaction tube by using a substrate processing apparatus comprising: the nonmetal reaction tube; a heater that heats an interior of the reaction tube to a prescribed processing temperature; a metal flange for disposing the reaction tube thereon, that constitutes a furnace opening of the reaction tube; a furnace opening cover for covering the furnace opening of the metal flange; a gas introducing opening provided for the metal flange, for introducing a reaction gas into the reaction tube; and an exhaust opening integrally provided for the reaction tube, for exhausting the interior of the reaction tube.
A fourth invention resides in a method for manufacturing a semiconductor device, comprising forming a semiconductor device in a nonmetal reaction tube by using a substrate processing apparatus comprising: the nonmetal reaction tube in which a substrate is processed; a gas introducing opening for introducing a reaction gas into the reaction tube: a heater that heats an interior of the reaction tube to a prescribed processing temperature; a metal flange for disposing the reaction tube thereon via an O-ring, that constitutes a furnace opening of the reaction tube; a furnace opening cover for covering the furnace opening of the metal flange; a coolant flow passage provided for the metal flange, that allows a cooling medium for cooling the O-ring to flow therethrough; and an exhaust opening integrally provided for the reaction tube, for exhausting the interior of the reaction tube, wherein a gas after processing the substrate in the reaction tube is exhausted from the exhaust opening before passing through the O-ring.
According to the third and fourth inventions, since an exhaust opening is provided for a reaction tube disposed on a metal flange, a reaction gas is exhausted from the exhaust opening provided for the reaction tube before the reaction gas passes through an O-ring disposed between the reaction tube and the metal flange. Accordingly, the reaction gas which remains at a high temperature is exhausted from the exhaust opening without being cooled by contact with the metal flange which becomes cooled as the O-ring is cooled by allowing a cooling medium to flow. As a result, it is possible to effectively prevent reaction by-products resulting from the cooling from adhering to a periphery of the exhaust opening or an inner wall of the metal flange so that a high quality semiconductor device can be manufactured without any defects due to adherence of particles.